So far, reactors harnessing catalysts have been used in various fields, and they are best designed depending on what purposes they are used for.
On the other hand, use of hydrogen as fuel has recently attracted attention, partly because of no spewing of such global warming gas as carbon dioxide in terms of global environmental protection, and partly because of high energy efficiency. Fuel cells in particular have gained attention, partly because they can convert hydrogen direct into electric power, and partly because they are capable of high energy conversion efficiency in cogeneration systems making use of generated heat. The fuel cells have hitherto been used under more specific conditions: for space development, ocean development, etc., and they are now going as far as the development of automobiles, and domestic distribution power sources, and fuel cells for portable equipments are now under development as well.
For the fuel cells for portable equipments size reductions are essentially in need; size reductions of reformers adapted to modify hydrocarbon fuel with steam to generate hydrogen gas are under studies. For instance, there are various microreactors developed that have a microchannel in a metal, silicon, ceramic or other substrate with catalysts carried in it (JP(A)2002-252014).
With a conventional microreactor, an outer wall is often forced into a high temperature state of 200° C. or hither for the reasons of heating with a heat generator for keeping the desired endothermic reaction going on by a carried catalyst and heat generation from an exothermic reaction. When the microreactor is used with portable equipment or the like, therefore, it is required to insulate heat between the microreactor in the high temperature state and the surrounding devices or parts.
However, to locate a known heat insulator such as one formed of glass wool or ceramic material around the microreactor in the high temperature state thereby reducing the outer wall temperature of the insulator down to about normal temperature to about 50° C., that insulator must have a large thickness, offering a problem that it cannot practically be used for portable equipment for which size reductions are demanded.